Fountain pen



FIG. 1 is a right side elevational view of a fountain pen showing my new design;

FIG. 2 is a left side elevational view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a perspective view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a top view thereof. 

The ornamental design for a fountain pen, as shown. 